Why does rearranging the batteries in a dead remote control (or any other DC device) temporarily (sometimes) revive it?
It scrubs a bit of oxidation off of the contacts.
A small piece of Scotch Brite pad is hand for cleaning battery contacts. There are also fiberglass brushes made for the same purpose.
So I guess I should always try cleaning the contacts before replacing the batteries?
No, just replace them.
If the batteries are so dead that a bit of oxidation is preventing the remote from working, it’s probably time for new ones.
If you don’t have spares on hand, sure, give it a try. Nothing to lose.
You don’t have to rearrange the batteries. Usually just rotating them around a bit while leaving them in place will do the trick.
But yeah, if they are so close to dead that a tiny bit of oxidation is enough to make them stop working, you are probably best to just replace them at that point.
I’ve found the classic “percussive maintenance” is often enough to get the job done in this situation. This is particularly handy for certain remotes that use a screw on the battery compartment door instead of an easy-to-open spring tab. A good smack or two jostles the batteries in their compartment, restoring electrical continuity.